A Virtual Cache for Overlapped Memory Accesses of Path ORAM

Naoki Fujieda, Ryo Yamauchi, Hiroki Fujita, Shuichi Ichikawa

Abstract

Oblivious RAM (ORAM) is a technique to hide the access pattern of data to untrusted memory along with their contents. Path ORAM is a recent lightweight ORAM protocol, whose derived access pattern involves some redundancy that can be removed without the loss of security. This paper presents last path caching, which removes the redundancy of Path ORAM with a simpler protocol than an existing method called Fork Path ORAM. By combining Delay and Reuse schemes, the performance of our technique was comparable with Fork Path ORAM. According to our evaluation with a prototyped FPGA implementation, the number of LUTs used with the last path caching was 1.4%-7.8% smaller than Fork Path ORAM.